EXOA2

Disk instability remains the leading formation pathway for some of observed giant planets. In particular, this model can more naturally explain giant planets at large separation, giant planets around M stars, and very young giant planets. However, there are still many open questions regarding this formation mechanism, and the expected population of planets.
We are working on a new disc instability population synthesis (DIPSY) that aims to address these questions and make predictions about the expected population of planets that can be tested observationally.
We find that fragmentation (the formation of bound clumps in the disc, a necessary condition for planet formation in the disc instability model) depends sensitively on the precise physics during the disc formation (infall). We show that infall models that form discs compatible in size with observed young discs are likely to fragment, though this may happen only in a minority of systems. Furthermore, we demonstrate how the intrinsics of orbital migration, mass accretion and clump interaction influence the fate of the formed clumps.
The figure shows the fraction of systems that fragment as a function of the final stellar mass for different parameters studied [1].
The results of the population synthesis, combined with current and future observations, will deepen our understanding of planet formation irrespective of the formation model.

Fig. 1: Fraction of fragmenting discs as a function of the final stellar mass for different parameters. When an infall model motivated by non-ideal MHD simulations is applied, no fragmentation occurrs. In contrast, infall informed by radiation hydrodynamic simulations leads to a substantial fraction of discs fragmenting, especially at higher masses.

References:

[1] Schib, O., Mordasini, C., Wenger, N., Marleau, G. D., & Helled, R. 2021, Astronomy and Astrophysics, 645, A43

How to cite: Schib, O., Mordasini, C., and Helled, R.: DIPSY: A New Disc Instability Population Synthesis, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-50, https://doi.org/10.5194/epsc2022-50, 2022.

New ALMA observations of protoplanetary disks allow us to probe planet formation in other planetary systems, giving us new constraints on planet formation processes. Meanwhile, studies of our own Solar System rely on constraints derived in a completely different way. However, it is still unclear what features the Solar System protoplanetary disk could have produced during its gas phase. By running 2D isothermal hydro-simulations used as inputs for a dust evolution model, we derive synthetic images at millimeter wavelengths using the radiative transfer code RADMC3D. We find that the embedded multiple giant planets strongly perturb the radial gas velocities of the disk. These velocity perturbations create traffic jams in the dust, producing over-densities different from the ones created by pressure traps and located away from the planets’ positions in the disk. By deriving the images at λ = 1.3 mm from these dust distributions, we show that very high resolution observations are needed to distinguish the most important features expected in the inner part (<15 AU) of the disk. The traffic jams, observable with a high resolution, further blur the link between the number of gaps and rings in disks and the number of embedded planets. We additionally show that a system capable of producing eccentric planets by scattering events that match the eccentricity distributions in observed exoplanets does not automatically produce bright outer rings at large radii in the disk. This means that high resolution observations of disks of various sizes are needed to distinguish between different giant planet formation scenarios during the disk phase, where the giants form either in the outer regions of the disks or in the inner regions. In the second scenario, the disks do not present planet-related features at large radii. Finally, we find that, even when the dust temperature is determined self-consistently, the dust masses derived observationally might be off by up to a factor of ten compared to the dust contained in our simulations due to the creation of optically thick regions. Our study clearly shows that in addition to the constraints from exoplanets and the Solar System, ALMA has the power to constrain different stages of planet formation already during the first few million years, which corresponds to the gas disk phase.

How to cite: Bergez-Casalou, C., Bitsch, B., Kurtovic, N., and Pinilla, P.: Constraining giant planet formation with synthetic ALMA images of the Solar System's natal protoplanetary disk, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-85, https://doi.org/10.5194/epsc2022-85, 2022.

Transition disks are one of the enigmas of the planet formation process: These objects typically feature wide gaps in the dust component, along with deficit of NIR emission corresponding to a lack of small grains in the inner regions, but simultaneously require a gas rich inner disk capable of sustaining high accretion rates, and a high content of pebble sized grains to explain the emission detected in the millimeter continuum.
Massive planets of several Jupiter masses have been long proposed as an explanation for these objects. However, despite the efforts to find these giants, only one or two disks have confirmed detections of a planetary companion. We propose a new hybrid model that easily explain the properties of transition disks, by combining the contributions made by different research groups over the last decade in photoevaporation, dead zones, and dust trapping. In our model photoevaporation takes care of opening a cavity in the gas and dust component, while dead zones in the inner regions lead to long lived-inner disk, capable of sustaining the observed accretion rates during the photoevaporative dispersal process. Finally, dust trapped in moderate substructures (such as the ones caused by small Saturn mass planets) can explain the emissions found in the millimeter continuum, without imposing strong constrains on the planet location.
With our model we show that instead of invoking massive fine-tuned planets to explain all the transition disk properties, the different processes that occur in protoplanetary disks complement each other and naturally reproduce the transition disk observations. Then, perhaps the reason of why we don't find more hidden massive planets is, simply, because they are not there.

How to cite: Gárate, M., Pinilla, P., Birnstiel, T., Ercolano, B., Stammler, S. M., Picogna, G., Delage, T. N., Stadler, J., Franz, R., Andrews, S., and Miotello, A.: Explaining transition disks without massive planets, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-271, https://doi.org/10.5194/epsc2022-271, 2022.

AB Aur is a bright and young Herbig Ae star surrounded by a broad transitional disk, with a long record of detailed observations at various wavelengths. Multiple direct and indirect evidences for the presence of embedded proto-planets have been reported in the recent years in this system. A prominent double spiral pattern was first detected with ALMA in the molecular line emission of CO gas, with a large pitch angle in the most inner region, suggesting the presence of at least one sub-stellar body within the cavity of the dusty disk (R<120au). We obtained two epochs of observations of AB Aur with VLT/SPHERE (Dec. 2019 - Jan. 2022). The first polarimetric image showed a wealth of structures at several scales. Two spirals clearly overlap those detected with ALMA, although with a higher angular resolution. One of these spirals features a twist located at 0.18’’ from the star, reminiscent of structures predicted by the theory of density waves produced by a gravitational perturber onto the gas distribution. The analysis of the multi-epoch data shows changes consistent with Keplerian rotation with a protoplanet located at about 30au from the star. In addition, localized emissions could be attributed to additional planet candidates (which are otherwise expected in order to carve the large disk cavity), including the recent claim of a super-Jupiter near 90au from high-contrast near-IR imaging with Subaru-SCexAO. All these pieces of evidence make AB Aur one of the most promising young sources to investigate planet-disk interactions, and to unveil the close environment of accreting planets. I will report on the global (and detailed) analysis of the new observational results for this nascent planetary system, both in the context of the multi-epoch, and multi-wavelength SPHERE+ALMA images, and with the contribution of multi-fluid hydrodynamical simulations. 

How to cite: Di Folco, E., Boccaletti, A., Dutrey, A., Tang, Y.-W., Guilloteau, S., and Pantin, E.: How many forming planets in the transitional disk around AB Aurigae ?, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-313, https://doi.org/10.5194/epsc2022-313, 2022.

Observing dynamical interactions between planets and disks is key to understanding their formation. Two protoplanets have recently been observed within PDS 70's transition disk, along with an extended signal towards the north-west of the star. In this contribution, I will present a temporal analysis of the PDS 70 disk morphology with the aim of assessing whether it could trace a spiral arm caused by the dynamical interaction between the planet PDS 70 c and the disk - or rather be the footprint of a vortex, which can mimic a spiral-arm in an inclined disk. I will show the PDI and ADI images obtained with SPHERE-IRDIS spanning 6 years of observations. We reduced PDI datasets through the IRDAP polarimetric data reduction pipeline (for PDI data) and a novel algorithm that we developed (MUSTARD, for ADI data). I will explain the principle of our inverse-problem based MUSTARD algorithm. I will then show the trace of the potential spiral that we inferred by identifying local radial maxima in azimuthal slices of the disc in each dataset. I will then compare the measured traces with the expected motion of a spiral launched by planet c - i.e. in rigid-body motion. I will show how the traces seem to perfectly align in all datasets, and will finally discuss the implications of our results on the nature of this extended feature.

How to cite: Juillard, S., Christiaens, V., Absil, O., and Benisty, M.: A Spiral arm or a Vortex in the outer disk of PDS-70 ?, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-942, https://doi.org/10.5194/epsc2022-942, 2022.

Disk winds and planet-disk interactions are considered to be two of the most important mechanisms that drive the evolution and dispersal of protoplanetary disks and in turn define the environment in which planets form and evolve. While both have been studied extensively in the past, we combine them into one model by performing three-dimensional radiation-hydrodynamic simulations of planet-hosting disks that are undergoing X-ray photoevaporation, with the goal to analyse the interactions between both mechanisms and to produce synthetic observations of common disk and wind diagnostics that could serve as observational tools for testing the interactions between the planet, the disk and the wind in our models.

The models show that a cavity in the gas disk that is carved by a sufficiently massive planet can significantly affect the structure and kinematics of a photoevaporative wind. This effect can be strong enough to be observable in commonly observed wind diagnostic lines, such as the [OI] 6300 Å or [SII] 6730 Å line, which we model with detailed photoionization calculations. When the disk is observed at inclinations around 40° and higher, the synthetic spectral line profiles may exhibit a peak in the redshifted part of the spectrum, which cannot easily be explained by simple wind models alone. Moreover, massive planets can induce asymmetric substructures within the disk and the photoevaporative wind, giving rise to temporal variations of the line profiles that can be strong enough to be observable on timescales of less than a quarter of the planet's orbital period.

How to cite: Weber, M., Ercolano, B., and Picogna, G.: Modelling the interplay between protoplanetary disks, planets and X-ray photoevaporative winds: Observational diagnostics, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-1074, https://doi.org/10.5194/epsc2022-1074, 2022.

The ability of protoplanetary disks to form planets depends on the evolution of their bulk (dust) mass reservoir. Surveys of nearby star-forming regions have revealed that there is a time dependence on the disk dust mass. In different regions in the Orion molecular clouds, meanwhile, the photoevaporation of disk material by nearby young O-type stars is clearly visible. However, the evolution of disk masses as a function of the FUV radiation field is not usually studied empirically, and its influence around fainter, but more common, B-type stars is not well constrained by observations.

In this contribution we take an empirical view of the impact of external FUV fields on the evolution of protoplanetary disks in Orion, by using existing surveys in the Trapezium and NGC 2024 clusters, and the new N = 873 Survey of Orion Disks with ALMA in L1641 and L1647. Together, these observations allow us to confront model predictions, and provide a constraint on how commonly external photoevaporation determines the evolution of planet-forming material in the first megayears.

How to cite: van Terwisga, S. and Hacar, A.: Protoplanetary disk mass loss near O- and B-type stars: an empirical view, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-1142, https://doi.org/10.5194/epsc2022-1142, 2022.